High Tech Materials in Boat Building
The Pros and Cons of Space Age
Materials in Boat Building
What it Means for the Consumer
by David Pascoe, Marine Surveyor
The boat building industry has entered an
unprecedented period of experimentation of new materials for use in the
fabrication of what were once called fiberglass hulls. Those of us who have
been around the boat building scene for a while have seen a lot o f new ideas
and materials come and go over the years. Some have met with success, but most
have met with failure, or one way or another have proved unsuitable for
building production-line boats.
In this article, we'll take a look at where the industry has been, where it
is likely to go, and what effect these changes are likely to have on the end
user, the boat owner. We'll look at some questions such as whether the term
caveat emptor now more appropriate than ever. After 40 year of fiberglass boat
building, is there really a need to take a risk with new, untried materials?
Does the use of such exotic new materials really offer the boat owner any real
benefits? My answer is no, they usually don't, and I will explain why.
Increasingly, we find a new term being introduced to define what we once
called a plain fiberglass hull, "composites." Composite merely means the
combination of two or more materials to make a whole. Fiberglass, a
combination of plastic resin and glass fibers, is a composite. But, in the
marine industry, composite increasingly comes to mean the use of a third
material, a core material such as balsa or foam.
Hurricane Andrew help surveyors to evaluate new materials and construction
methods, putting boats like these to the ultimate test. Here we find out
whether the advertising claims meet the tests of reality.
The side of
this 42 Bertram took out two 12" diameter wood pilings and crushed another
boat without ever breaching the full. The tremendous beating that this boat
took proves beyond any doubt the superiority of solid fiberglass laminates.
Boat buyers should be aware of several important points when considering
the purchase of a new boat. The first is that new resins, reinforcements and
core materials are being developed at an unprecedented rate. Industry
magazines and trade shows are promo ting a dizzying array of new materials.
Foams laced with plastic and aluminum honeycombs, new arrangements of glass
fiber reinforcements in an apparently endless array of new weaves and fiber
configurations, plus a wide array of new plastic resins and c hemical
additives, are being widely promoted.
material called CoreMat(TM), this hull fared poorly
from contact with a weak 4" x 4" dock piling. The outer laminate is extremely
thin (less than 1/8") and had little or no adhesion to the foam. We swung a
carpenter's hammer at this hull side with only moderate power and it went
right through the hull side.
cored 60' Hatteras hull was subjected to the ultimate test. Not only did it
take out two 16" pilings, but look what it did to the concrete sea wall. The
outer laminate was breached but the inner laminate remained intact. Compare
this wit h the damage caused by a 4" piling in the photo above. The yacht was
capsized by 175 MPH winds in the tuna tower, otherwise it would not have sunk.
The second point is that the boat building industry, as a whole, performs
very little research and development into the materials it selects and
utilizes for hull construction .It is important to understand that proper R &
D of a new material is extraordinarily expensive and take as long as 3-5 years
to test and prove the application of new materials. Therefore, because of the
extreme cost, the past history of the industry has been to try a new material
first and ask questions later. Over the years, numerous builders have
incorporated untried, untested materials in their product lines, thus making
guinea pigs of their customers. And it is this lack of R&D that, in the past,
that has been responsible for so many of the hull failures that have plagued
As long as thirty years ago, the marine industry learned the hard way why
it was not a good idea to use balsa cores on hull bottoms. Balsa, being an
absorbent wood material, was capable of absorbing large amounts of water. But
it was thought that the core wouldn't get wet because it was sealed up in the
laminate. Of course, with the advent of the hull blistering problems, we now
know that even seemingly solid laminates can absorb water.
That old knowledge seems to have been lost as builders are once again
coring hull bottoms, only this time with plastic foam. The idea, apparently,
is that foam won't succumb to water absorption and other problems that were
encountered with balsa. Materials suppliers claim that because foam has
"closed cells" that the material won't absorb water. Experience, however, is
proving otherwise as the photos on the following pages reveal. Water ingress
into foam cores has proven a common occurrence which, once i t does, can
result in very rapid deterioration of hull strength.
While many of these new materials grab center stage attention at trade
shows, seminars and in magazine articles, promoting the many virtues, what
attracts my attention is the lack of any test data to go along with these new
materials. I am reminded of the introduction of closed cell foam back in the
early 1980's as the new miracle material for boat builders that was hyped as
the ideal material for building boats that were stronger, lighter and less
costly to build. Having once worked in a plant that built balsa cored hulls, I
was well familiar with the technical data on balsa, including its strengths
and weaknesses. What caught my eye, even back then, was that, of those few
foam makers or distributors who even bothered to offer spec sheets on their
mate rial, virtually all that I had seen had selectively provided only the
most complementary data on their product. In other words, they sold the
materials strengths while never mentioning its weaknesses. The result was that
a few boat builders jumped onto the foam core bandwagon with disastrous
results. Massive core failures were endemic to nearly everyone who initially
Here was a case where builders latched onto a material without even knowing
what it is structural properties were. They took the salesman's word and tried
the material directly in their product line, without performing their own R&D.
When massive hu ll failures resulted, many of these companies folded up
because they couldn't meet their customers claims.
bonding of the core to the outer hull is one of the major problems encountered
with foam cored hulls. In this case, less than 50% of the core was bonded,
resulting in complete delamination of the full. Even where the bonding agent
made contact with the core, adhesion was poor to nonexistent.
pouring out of this hull is the result of complete water saturation of the
foam core. Hydraulic action - panting of the inner and outer skins -
pulverized the foam and turned to black mush. Once the foam degraded, the
laminate weakened and s plit open, sinking the boat.
Many of the larger builders such as Bertram, Hatteras and Viking make a
valid attempt at R&D. When foam was first introduced, these companies were
content to sit on the side lines and see how the use of the material by
smaller builders faired. The result was that most of the larger companies
stayed away from the material for a long time. Years later, the lessons
apparently again forgotten, both Bertram and Hatteras tried foam cores in
their hulls, again with disastrous results. Hatteras ended up recalling one
full model line in which they used foam in the hull. Fortunately, they
discovered their error after only eight boats were built. Bertram also tried
the material on a more limited basis and they, too, immediately encountered
I witnessed one of the most startling examples of materials ignorance by a
manufacturer while attending a product demonstration at a prestigious custom
yacht builders plant. With the outer skin of the hull freshly laid up, the
core material manufacturer proceeded to demonstrate how their new core bonding
putty would solve the problem of incomplete bonding of the core to the
laminate. They even used a special vibrating machine on the core to ensure
that the bonding putty was fully spread out and worked into all the seams of
the core. After completing the process, to demonstrate just how thorough the
bonding would be, they pulled the freshly applied core away from the laminate.
Viola! Only about 70% bonding took place, leaving large areas completely out
of contact with the bonding putty, and the demonstrators red-faced.
But the salesmen recovered quickly and told the audience that this was just
a demonstration, but that if you do it right, you'll get the right
results. The audience was not quite so sanguine. We were left to wonder, if
the experts couldn't get it right the first time (after all, it was their
product), how were us lesser mortals supposed to do any better?
The answer was, of course, that they couldn't, as the nearby photo
testifies to other builder's experience with the product. As it turned out,
bonding failures with this product became a regular feature of its
Then there was the case of Airex, a widely touted foam whose use came and
went as rapidly as the changing of the seasons. Airex was a different type of
foam than the typical rigid urethane foams that we usually hear about. Here
again, a new material was promoted without R&D. A PVC based material, that is
highly sensitive to heat, no one bothered to find out how this material would
react to heat. Used on decks that heat up or on hull sides in way of hot
engine rooms, Airex foam would soften, resulting in laminate distortion and
By now, everyone is familiar with the problems of hull blisters. But
perhaps you were not aware that for the first twenty years of fiberglass boat
construction, very few boats ever encountered the problem. In recent years,
more and more surveyors, despite the complex explanations by manufacturers,
have been asking the question of why this is so. The answer is astonishingly
simple: inferior materials. A high production builder uses millions of pounds
of plastic resin annually. If they could reduce the cost of their resin by as
little as 10%, they could achieve enormous savings. And that's what they did
by using a lower quality resin that significantly cut their materials cost.
The hull blistering problem then blossomed into existence and continues to
Back in the late 1970's there were two builders who attempted to use two
different types of honeycomb core. Yes, on the hull bottoms. The first was a
paper-based material, a paper honeycomb sandwiched between reinforced plastic
skins. This material was tried out by the builder of a very expensive 26 foot
sport fisherman. It doesn't take much imagination to figure what happened to
these boats. Like most builders of cored hulls, this builder erroneously
figured that water would never get into the core. A nd when it did, the result
The second new core was an aluminum core. Once sea water got into this
foil-thin aluminum honeycomb, the rate of destruction was nearly as fast as
with the paper core. Within a few years time, these boats experienced
catastrophic bottom panel failure. Now here's the real rub: because the
builder was told that the use of the core would make the bottom panels much,
much stronger, the builder then chose to greatly reduce the size of the
framing system. Thus, when the bottom core failed, the loss of the core
strength resulted in the loss of strength of the entire structure. The weak
framing system caused the entire bottom structure to fail, whereas had the
framing system been up to normal standards the extent of failure would have
been far less dramatic th an it was.
If you're contemplating the purchase of a new or used boat, the sort of
problems outlined above are exactly the kind of thing you want to avoid. When
issues of serious hull problems arise, resolution of the problem is rarely as
simple as returning the product to your nearest dealer for a refund. Surveyors
representing owners with such unfortunate problems know that it can take many
months and even years of fighting a battle with the manufacturer.
Since solid fiberglass hulls have been successfully built for over 40 years
now, the question arises as to whether there is really any significant benefit
to coring a fiberglass hull. Are cored hulls really stronger and lighter than
solid cored hulls? We've all heard the claim that cored hulls are lighter and
stronger than solid laminates, but this is not exactly true. Cored laminates
are stronger in flat panels, but are weaker when used with curved surfaces. My
examination of hundreds of boat hulls damaged by recent hurricanes clearly
shows that most cored hulls fared nowhere near as well as solid laminate
Here's a good example. In one case, an older, solid fiberglass 42' Bertram
and a custom built, cored hull 42 footer were docked side by side. The
hurricane broke both boats loose and drove them across a bay where they were
both badly battered against a concrete embankment along with a group of other
boats. Both of these yachts sustained the identical degree of battering. Can
you guess which one held up the best? In fact, the cored hull yacht had nearly
50% of its hull destroyed and was sunk. The Bertram, on the other hand,
despite an incredible battering, never had its hull breached and survived the
storm without sinking.
You might be asking why you should care how well your boat holds up in a
hurricane? The answer is that you would care if you were in it when it ran
aground or was in a collision with another vessel, deciding the question of
whether you and your family would sink or swim. Poorly constructed hulls not
only perform poorly in storms, but under more ordinary adverse conditions as
A case in point occurred years ago when I smacked my boat into a 12" steel
I-beam waterway marker at night. No foam cored hull would have stood up to the
impact that my solid fiberglass hull withstood without ripping a hole in the
hull. There's no doubt in my mind that me and my friends would have gone
swimming that night were we in a foam cored hull.
The fact is that foam cored laminates are extremely vulnerable to impact
damage, and are highly prone to core separation. Our examination of balsa
cores revealed that they, too, fared much better than foam cores. The
advantage of balsa is that it has both superior bonding strength and superior
shear strength. Whereas foam is very weak against inter laminar shearing
forces, balsa is quite strong. This is easy to understand because we all
understand how wood is weak with the grain, but very strong again st the
We have all heard the hype that foam cored panels are stronger than solid
laminates. What you may not have heard is that cored panels are only stronger
if they are flat! Curved cored panels are decidedly weaker than solid glass
panels, particularly when compressive loads are applied in shear mode. Most
foam cored panels take very poorly to bending. The "S" shaped reverse curves
of the typical sailboat hull is a case in point, and accounts for why so many
failures occur in sailboats. Here we see that the shape of the panel has
everything to do with the performance of cores.
The effect of
stress and compression loading on foam cored panel. Bending causes inner and
outer skins to creep at different rates due to the difference in the radius,
causing the core to shear or separate.
To understand what happens to curved panels, imagine an "S" shaped panel
like a sail boat hull section. Now, apply a compressive load on the ends as
shown opposite. What happens? Well, the inner and outer laminates bend and
creep at different rates, owing to the fact that they have a different radius.
This causes a very unexpected shearing force that shears the very weak foam.
This, in a nutshell, demonstrates why so many foam core failures occur on
curved surfaces as compared to flat panels. The shear strength of the foam is
simply inadequate to resist these forces.
What should now be giving us pause for reflection is the fact that both
paper, plastic and aluminum cores are once again being marketed to boat
builders. Some of these are in different configurations, such as aluminum
honey comb embedded in foam. Others consist of open cell molded plastic
honeycomb, or foam-filled plastic honeycomb. Such materials are probably fine
for use in non-dynamic structures, but how are they going to hold up in a
dynamic structure such a boat hull that is constantly immersed in sea water
that travels at high speed? Do the builders have the test data to warrant
their use? Whenever I ask this question of materials distributors, it is
usually met with a blank stare, telling me that they have no idea of the
physical characteristic s of the material they're marketing.
The use of such so called "high tech" materials is spreading rapidly in the
boat building industry once again and the axiom caveat emptor is now
more appropriate than ever. The question we need to ask ourselves is, knowing
that good quality fiberglass hulls have been built for over forty years with
an excellent track record of success, is there any real need to take a risk
with new, untried materials? Does the use of such exotic materials really
offer the boat owner any real benefits?
My answer to that is no, they don't. The move to incorporate such materials
in boat hulls is primarily an effort to reduce materials cost and produce a
cheaper product, one that ultimately poses higher risks of hull failure and
produces boats that are les s rugged with a shorter life span. They offer the
boat owner no significant benefit, but plenty of extra risk. The most
significant risk of the utilization of untested materials in boat construction
to the boat owner is the potential for serious hull failures for which the
boat owner has difficulty in getting the problem resolved.
Over the years, many builders have gotten themselves into so much trouble
using unproven materials and techniques that financially they were unable to
fulfill their warranty commitments, went bankrupt and left their customers
holding the bag. This is precisely the sort of thing we wish to avoid.
The following are a few tips on how to avoid falling into the trap of purchasing
an inferior product.
- Be aware that boat building is a low capital investment manufacturing
business that is easy to enter but hard to prosper in. During the last ten
years, an estimated 80% of all builders went under, most leaving unresolved
warranty claims. If warranties a re important to you, choose your builder
- When shopping for new or used boats, beware whenever the price of one
builder's boat, as compared to a group of other similar boats, is
substantially less. Quality is universally a function of price. Whenever the
price of one boat appears to be too goo d to be true, it usually is. Chances
are the reason is low quality.
- Take the time to consider the quality of vessel you wish to purchase.
Today more than ever, boats are designed to appeal to vanity, often at the
expense of quality, safety and resale value. Determine how long you think
you will own the vessel, and what is it likely be worth when it is time to
sell. Remember that lower quality boats deteriorate and depreciate more
rapidly than higher quality boats. Price should not be the only determining
- Use the top quality builders such as Bertram, Hatteras and Viking as the
benchmark for comparison.
- Once you've decided on the type of boat you're interested in, but before
actually shopping the market, contact one of the surveyors listed on this
page and discuss the various types of boats that you are considering. Our
surveyors are usually familiar w ith the construction of the most popular
builders and they will be happy to share with you their knowledge.
- Once you've determined which particular vessels you are interested in,
it is worth a call to the builder to find out whether their hulls and decks
are cored and, if so, with what materials.
Experienced boaters are increasingly learning the advantages
of having even new boats surveyed. Nobody is perfect and even the best of
builders can, and do, make mistakes. A truly professional marine surveyor
knows how to evaluate hull construction and pu t a boat through its paces in a
rigorous check out regimen, thereby making the outfitting and delivery process
as efficient and smooth as possible. A new boat survey accomplishes the
- Discover faults and defects prior to taking delivery.
- Saves time and repeat trips to the dealer for warranty repairs.
- Provides the buyer with negotiating leverage that he might not otherwise
have without the survey.
- Correct design or engineering mistakes that may not reveal themselves
until after the warranty period has elapsed.